Transparent plastic articles, for example, molded articles of amorphous thermoplastic resins, such as polycarbonate, polymethyl methacrylate, cellulose butyrate, polyvinyl chloride an polystyrene, have heretofore been considered to be applicable, in various fields, as substitutes for glass articles because of their transparency and light weight thereof. However, they are easily scratched and tend to lose the transparency. Therefore, they are actually utilized for limited applications. Consideration has been given to eliminating such undesirable characteristics of plastic articles by forming a transparent protective layer on the surface of the articles by the use of coating materials, but the conventional coating materials did not result in sufficient improvement.
For instance, the specification of U.S. Pat. No. 3,451,838 proposes coating the surface of an acrylic resin or polycarbonate resin molded article with a composition comprising a mixture of methyltriethoxysilane and phenyltriethoxysilane and then effecting the curing. However, surface-coated plastic articles obtained according to this method are inferior as to scratch resistance, and hence, their uses are still limited.